Using molecular ozone to destroy prions: A new method for preventing infection?

An effective method for the decontamination of infectious wastes has recently been investigated by a Canadian research team, one which is hoped to provide more thorough sanitation procedures for a variety of settings, including hospitals, water treatment facilities, and slaughterhouses. This method involves the use of molecular ozone, and appears to be effective in the destruction of prion proteins, which can be particularly difficult to inactivate using other procedures. The study has direct implications for the prevention of pathogenic outbreaks of various brain disorders in both human and animal species.

Prions are infectious agents which consist entirely of protein; their lack of any nucleic acid component makes them distinct from other sources of infection. Under normal circumstances, these misfolded proteins play loosely defined roles in cell-cell adhesion and intracellular signaling processes. Cell membrane-anchored prions exist in a variety of tissues, and their elevated levels in the brain suggest that they likely play a role in neuronal communication as well. Normal cellular prion protein (PrPC) can transform into a different, pathological isoform (PRPSc), which is characterized by resistance to proteolytic degradation and great capacity for infection. These infectious attributes stem from the ability of PrPSc to induce the template-directed misfolding of normal prions, since aggregates of the misfolded isoform in a host can lead to various neurodegenerative diseases, including bovine spongiform encephalopathy (mad cow disease).

Prion proteins are of particular concern with regard to their resistance to typical decontamination procedures such as ultraviolet irradiation, chlorination, and formalin treatments. These treatments are typically utilized to treat drinking water and decontaminate sewage, but suffer from a reduced capacity to eliminate prions from these sources. Since prions can be sequestered in groundwater or soil for a long period of time whilst retaining their infective properties, advances in water treatment strategies which can remedy this treatment gap would be highly advantageous from a public health perspective. In particular, modern industrial procedures which produce a large amount of animal waste could be handled in a much safer manner if more adequate sanitation practices (including the removal of prions from these wastes) were developed.

The goal of this recent study was to investigate the ability of molecular ozone to act as a potential decontamination agent for these pathogenic molecules. Ozone has been used previously as an effective oxidative sanitation technique through its collective actions on bacterial, protozoan, and viral species. Though it has also been shown to reduce the number of active PrPSc molecules as well, the nature of this interaction is not well understood. To address this discrepancy, the research team used ozone to inactivate a specific type of PRPSc, one which can result in an infection of scrapie (an encephalopathy which affects sheep and goats).

The results of the study were very promising, as ozone appeared to eliminate the infectious prions from aqueous sources at relatively low concentrations.

“Although we know that they have a very high-level resistance, it’s possible that we’ve discovered their Achilles’ heel,” said Norm Neumann, one of the leaders of the research project. “This means there might be simple solutions to dealing with contaminated medical instruments and waste products from slaughterhouses.”

One of the difficulties in tackling this project stems from the fact that, to eradicate prion proteins, the researchers were forced to utilize methods which would specifically act by denaturing protein components. Whereas decontamination methods such as UV irradiation target nucleic acids, the denaturation of proteins can require significant changes to pH and temperature, or large inputs of energy. Throughout the study, the researchers provide a rough blueprint for the specific conditions required to eliminate prions from a given source, and develop a set of specific requirements for this decontamination technique. Ultimately, they suggest that methods which utilize molecular ozone could be not only effective, but realistically applicable in a number of industrial or health-related settings.

“Because ozone is already commonly used in the hospital environment, the technology for this disinfection process already exists,” says Neumann. “It is possible to take a medical instrument, put it in an ozone bath and very quickly destroy 99.99% of the prions that are there.”

Thus, the effects of PrPSc on the conformational misfolding of proteins (and possible pathogenic outbreaks of numerous brain disorders) could be eliminated. Of note, the ability to prevent bovine spongiform encephalopathy (cattle), scrapie (sheep and goats), and chronic wasting disease (deer and elk) should be of particular relevance to industries which deal with large numbers of animals in close proximity. As numerous encephalopathies can affect human hosts as well, this research also appears to be immediately relevant to decontamination procedures utilized in the healthcare industry.